WASHINGTON 
Millions of passengers in cities across the U.S. ride old subway cars like the ones that crumpled in the deadly crash in the nation's capital. The largest transit systems depend on such cars for more than one-third of their fleets, despite safety concerns expressed by federal investigators more than three years ago.

In the earliest stages of the investigation into Monday's subway accident in Washington, which killed nine people and injured more than 70 others, the National Transportation Safety Board focused on why the passenger compartments within the subway cars fared so poorly. The demolished train cars spent much of Tuesday frozen on the tracks, one with metal peeled apart sitting on top of another nearly fully flattened on impact.

The NTSB raised alarms in March 2006 about older model subway cars after one of the cars in Washington's system collapsed like an accordion in a 2004 accident. The safety agency urged the Federal Transit Administration to develop crash standards that would address the telescoping of older cars and come up with a plan to remove aging trains that couldn't be structurally reinforced.

Washington is among the seven largest transit systems that rely on older cars in poor or marginal condition for more than a third of their fleets, according to a federal study published this spring that had been requested by a dozen senators, including then-Sen. Barack Obama. The others are in Chicago, Boston, San Francisco, Philadelphia, New York and suburban New Jersey. The older cars are either near or past their usefulness, the report said.

Old subway cars experience the worst damage – a loss of what the NTSB calls "survivable space" – in crashes because most aren't adequately reinforced for impact.

Debbie Hersman of the NTSB said Tuesday that the problem remains.

Transportation officials for decades have debated whether the federal government should have more oversight of local rail systems, but it's largely up to states to set their own standards. States often don't have the money or expertise to carry out that responsibility, government investigations have found. And a 2006 Government Accountability Office report said the FTA hadn't set goals for the safety program or come up with a way to track state performance.

A leading senator on transportation issues, Jay Rockefeller, said he was surprised to learn after Monday's crash that the NTSB can make recommendations to improve transit safety but doesn't have oversight authority, nor does the Federal Transit Administration.

"There's no authority to tell them they've got to run a safe train," said Rockefeller, D-W.Va., chairman of the Senate Commerce, Science and Transportation Committee.

FTA spokesman Paul Griffo said federal law bars the agency from regulating the operations of transit agencies, a prohibition that includes establishing rules on a rail car's ability to withstand a crash. FTA has supported trade groups that have developed and published voluntary standards, he said.

In Washington, Metrorail officials blame money. The system has 296 rail cars that were built more than 30 years ago, and it hasn't had enough money to cover the estimated $888 million needed to replace them, spokeswoman Candace Smith said.

But the agency's chief, John Catoe, said the system's trains were safe.

"Any crash at that rate of speed will have severe damage to the structure," Catoe said of Monday's crash, in which one train sped into the rear of another train that had stopped on the track.

Transit officials elsewhere in the country defended their trains, with some arguing their cars meet tough Federal Railroad Administration standards for crashworthiness.

Joe Pesaturo, a spokesman for the Boston area's Massachusetts Bay Transportation Authority, said that system's preventive maintenance program keeps its rail cars "safe and reliable at a reasonable cost."

The federal government said it will take more than $50 billion to bring commuter trains into good repair that serve Washington and the nation's other metropolitan areas, according to its report earlier this year. Obama's $787 billion stimulus program provides $8.4 billion for public transportation, which states are spending to buy new rail cars, build train stations and expand bus services.

The industry is working to make subway cars safer, said Martin P. Schroeder, chairman of the American Society of Mechanical Engineers' Rail Transit Vehicle Standards Committee. It has created its own crash standards for rail cars, but Schroeder noted that a subway car's crashworthiness is the passenger's last line of defense, since signals and operators are better positioned to avoid accidents.